PP and HDPE are the two highest-volume rigid commodity plastics, and they compete for many of the same parts. The deciding factors are usually stiffness, heat and cold.
Side by side
| Polypropylene (PP) | HDPE | |
|---|---|---|
| Stiffness | Higher | Lower |
| Heat resistance | Higher | Lower |
| Cold impact | Poor (homopolymer); good (impact copolymer) | Good |
| Density | ~0.90 (lightest) | ~0.94–0.97 |
| Living hinges | Excellent | Poor |
| Chemical resistance | Excellent | Excellent |
| Stress-crack resistance | Generally good | Varies widely by grade |
| Clarity | Translucent; clear with clarified random copolymer | Translucent to opaque |
Typical, general comparisons. Individual grades vary; check the data sheet.
Choose Polypropylene (PP) when
- You need stiffness, heat resistance or a living hinge
- Lowest weight per part matters
- Dishwasher or hot-fill use
Choose HDPE when
- Parts must stay tough in the cold
- Bottles, pails and crates that take abuse
- Pipe, tanks and film
PP homopolymer & impact copolymer · HDPE injection grades · Lighter parts · Tell us the grade you run now →